Apparatus for overhead submerged arc welding

ABSTRACT

An apparatus for overhead submerged arc welding has a hopper containing flux being pivotally mounted on a suspension for rotation about the suspension axis, the hopper having a bowl provided in the top part thereof, a welding head with a nozzle for supplying a consumable electrode, and means for supplying flux and pressing it against work. 
     The apparatus also has a forming means mounted for swinging in its longitudinal and transverse planes and for a vertical adjustment with respect to the work being welded. The forming means is in the form of a U-shaped body having its open top part facing towards the work being welded and legs having on the side of the nozzle a pair of diverging wedge-shaped projections, an adjusting bar being provided inside the body to extend length-wise of the joint being welded. Copying members in the form of four wheels are provided outside the body on either side of the legs thereof. 
     This construction of the forming means ensures maintenance of preset flux pressures at various points along the joint being welded.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the equipment for arc welding, in particular,and it deals with an apparatus for overhead submerged arc welding.

2. Description of the Related Art

A large volume of operations in the manufacture of welded structures iscarried out in welding rotatable annular joints of hollow structureswith a restricted access to joints being welded on the inner side of thestructure. Such joints include annular joints of closed vessels, annularjoints of pipelines, tanks, casings, field welds and shell plating seamsof ship hulls; longitudinal joints of large-area products which cannotbe positioned to facilitate welding. They also include joints ofdifficult-to-position webs, segments, three-dimensional and planarsections, and the like.

A submerged arc overhead welding method is characterized in that aconsumble electrode and a welding bath are turned at 180° in comparisonwith downhand welding. Flux an electrode are fed to the work from bottomup, i.e. as though towards a ceiling, the electrode being suppliedthrough a compacted flux.

This welding method is referred to hereinbelow as overhead submerged arcwelding.

This welding method is referred to as the overhead submerged arc weldingalso because the arc is in the body of metal.

So called overhead welds are produced as a result of such welding.

Overhead welds may be of different types, e.g. penetration overheadwelds, sealing overhead welds. There may be one-pass overhead welds andother types of overhead welds.

The penetration overhead welds are welds which are first to be producedin welding a joint and which are located in the top part of sectionsbeing welded on the joint side opposite with respect to the electrodesupply. Further welding of the joint, i.e. producing the necessarysubsequent welds is carried out by any appropriate known method, theelectrode being supplied on the same side as is the case with welding ofthe overhead penetration weld, e.g. the inner penetration welds ofrotatable annular joints of vessels, tanks, joints between bottomsections of shell plating of ships and other structures.

The overhead penetration weld arc welding allows, to a large extent, theoperation of welding from the interior of a vessel to be dispensed within welding rotatable annular welds, and welding in confined spaces inproducing straight welds of structures with a restricted access on theside of a ceiling can also be eliminated.

The sealing overhead welds are welds which are first to be produced inwelding a joint and which are located in the bottom part of sectionsbeing welded on the electrode supply side of the joint. Further weldingis carried out by any appropriate known method with the electrode supplyon the side of the joint being welded opposite to that used in theoverhead welding.

In practice, the penetration overhead welds are produced in weldingannular and longitudinal joints of structures with a restricted accessto joints being welded from the inside, the sealing welds being producedin welding longitudinal joints of difficult-to-position products, e.g.plate structures made out of segments, and other products.

One-pass overhead welds include welds produced in welding joints of alimited thickness arranged over the whole welded section. No furtherwelding of the joint on any side thereof will be required.

Welding of sealing and one-pass welds poses many problems concerned withthe formation of the surface of a finished weld.

During the overhead welding, the welding bath metal formed during arcingby fusion of the metal being welded, electrode material and flux isretained by a crust of partly melted flux and also by means of formingmembers. The forming members may be of various shapes and size and maybe made, e.g. in the form of plates, backings, bars, sliders and othermembers and structures.

Flux is pressed against the welding zone positively from bottom up and,as flux is being consumed, its stock is continually replenished. Forforming the top part of a weld, flux may be supplied both on the bottomside, through the gap between the edges of a product being welded, andfrom top by any appropriate known method by which a filled layer of fluxis formed. Special forming backings or flux holding means may also beused.

Numerous problems arise especially in welding hard to get at joints oflarge-size products of cylindrical or like configuration such as shiphulls and boiler units where especially high quality of welds isrequired and where the products must be rotated about their axis duringwelding operations, as well as in welding large-area planar productswhich it is very difficult to place in a position facilitating thewelding.

Known in the art is an apparatus for overhead submerged arc welding (SU,A, 469554), comprising a hopper containing flux and a bowl for supplyingflux thereto and for pressing flux against the work. The bowl has anoutlet port facing towards the joint being welded and an inlet port forsupplying flux to the bowl and for creating a desired pressure of fluxin the bowl. Flux is supplied by a pipe communicating with the inletport of the bowl. The pipe has a flux supply means in the form of anauger.

A welding nozzle through which the consumable electrode is supplied isprovided in the bowl adjacent to the inlet port and a pivotally mountedadjusting plate located downstream of the welding nozzle is provided onthe side of the bowl opposite to the inlet port.

For varying the angle of inclination with respect to the outlet port ofthe bowl, the adjusting plate has an adjusting screw.

This apparatus provided with the adjusting plate allows preset fluxpressure to be controlled during welding at different points along thejoint being welded.

During welding by means of this apparatus, the operator keep an eye onthe joint being welded and, if parameters of the joint, e.g. the amountof clearance between the edges of the structure deviate from presetvalues, the operator can correct the situation by acting upon the screwto vary the angle of inclination of the plate so as to maintain thedesired flux pressure since it is very important that preset fluxpressure values for high-quality overhead welding be maintained withmaximum possible accuracy at various points along the joint being weldedbecause otherwise the weld would be of poor quality.

The abovedescribed apparatus cannot, however, ensure an automaticmaintenance of preset flux pressure values at various points along thejoint being welded without operator's interference. During welding withthis apparatus, it is necessary to continually vary position of theadjusting plate so that the operator must be continually involved andmust pay a special attention during welding, the operator having to bevery skillful. Consequently, quality of weld in welding with the aid ofthis apparatus depends on the operator's skill and experience which maynot unfrequently result in low-quality welds.

In addition, the experience of operation of such an apparatus showedthat it is suitable for welding joints having minimum deviations ofparameters of their assembly before welding (e.g. misalignment of theplate edges, gap, V-section, etc.) and cannot be used for weldingelongated products or annular joints, especially of large-diameterstructures.

Known in the art is an apparatus for overhead arc welding (FR, B,2568808), comprising a hopper containing flux and accommodating a bowlhaving an inlet port and an outlet port, the inlet port communicatingwith a flux supply pipe. A welding nozzle for supplying a consumableelectrode is provided in the bowl. The bowl cooperates with a formingmeans having an adjusting bar for providing different pressures of fluxat various points along the joint being welded, a part of the formingmeans being located directly in the bowl, adjacent to the consumableelectrode.

The hopper supports a means for supplying the electrode to the weldingnozzle, and the hopper is mounted on a suspension by means of a pivotpin for rotation about this pivot pin and has a point-like contactcopying member which is located substantially in line with the adjustingbar. The adjusting bar also has a pair of copying members and is mountedfor longitudinal and transverse swinging movements.

In addition, the hopper is provided with a means for pressing the hopperproper and the copying member against the work being welded.

This apparatus for overhead welding can substantially automaticallymaintain the stability of flux pressures necessary for carrying outhigh-quality welding at various points along the joint being welded.Participation of the operator in controlling welding process issubstantially dispensed with, especially in welding elongated productsof a regular geometry (and more especially, of cylindrical and straightproducts), deviations from joint assembly parameters before weldingbeing compensated for.

This apparatus makes it possible to implement the method of overheadsubmerged arc welding in which different present flux pressure valuesare automatically maintained at various points along the joint beingwelded during welding so as to produce high-quality penetration overheadwelds.

This construction of the apparatus ensures a reliable retention of awelding bath during welding at the level of the joint being welded andthe formation of high-quality welds with the desired formation ofreinforcement on the inner side of the weld (on the side opposite to theceiling), i.e. in producing penetration overhead welds.

However, the welds produced in this manner have deviations of shape ofthe outer side of the finished weld admissible for the penetration weld,in the form of irregularities, undercuts, local weld width fluctuationsand other defects on the outer side of the weld which will requirefurther rewelding to provide a next layer.

These defects in forming the outer side of the weld can be explained byinadequate conditions provided by this apparatus for jamming andretaining flux at various points before the formation of welding bathand in the welding zone. In addition, this apparatus does not allowhigh-grade copying of the surface of the welded joint to be carried outdirectly adjacent to the point of welding which is necessary toproducing sealing overhead welds, and especially one-pass overheadwelds.

Moreover, this apparatus cannot provide maximum favorable conditions forcopying position of the working surface of the bar with respect to thesurface of the joint being welded in cases of a substantial deviation ofits surface from regular geometry. This is due to the relative positionof the copying members and their position with respect to the weldingbath which is not quite optimum as it is necessary for producing sealingand one-pass overhead welds. Investigations have shown that the copyingmembers should be located as close as possible to the welding bath(welding zone).

SUMMARY OF THE INVENTION

The main object of the present invention is to provide an apparatus foroverhead submerged-are welding in which corresponding construction of aforming means, an adjusting bar and copying members and their relativelocation with respect to a welding zone (welding bath) would allowautomatic welding of overhead welds, preferably back-up single-passwelds and, avoid conditions for jamming and retaining flux in thewelding zone, and creation and maintenance of preset flux pressure ondifferent parts along the joint being welded required for production ofhigh-quality welds with enlarged range of parts being welded which is(as during welding in the bottom position).

This object is accomplished by an apparatus for overhead submerged arcwelding, comprising a hopper containing flux pivotally mounted on asuspension for rotation about a pivot pin, having a welding headprovided with a nozzle for supplying a consumable electrode and meansfor supplying flux and pressing it against the work in the nozzle zone,a bowl accommodated in the hopper, the end of the nozzle for supplyingthe consumable electrode extending through the bowl, and a formingmeans, having an adjusting bar for providing preset pressures at variouspoints along the joint being welded, mounted on the suspension, havingcopying members, and mounted for swinging movements in the longitudinaland transverse planes of the forming means and for vertical adjustmentwith respect to the work. According to the invention, the forming meanscomprises a U-shaped body having its open top part facing towards thework, the legs of the body having, on the nozzle side, a pair ofdiverging wedge-shaped projection, the adjusting bar being providedinside the U-shaped body along the joint being welded, and the copyingmembers being placed outside the U-shaped body on either side of itslegs.

This construction of the apparatus in which the forming means is in theform of the U-shaped body makes it operable at high loads. The apparatusis versatile and can receive adjusting bars for providing preset fluxpressures at various points along the joint being welded, the bars beingvertically adjustable. The level at which the working face of theadjusting bar is located may be either below that determined by theheight of the legs of the U-shaped body (e.g. in welding joints withoutedge preparation) or above, e.g. in welding V-section joints where theworking face of the adjusting bar is in the form of a projection.

The working face here and below is the surface of the adjusting barwhich cooperates with melt in the welding bath and with the weld beingformed during welding.

In carrying out welding with minimum preset reinforcement of the weld,the level at which the working face of the adjusting bar is located maybe aligned with that determined by the leg height of the body, i.e. itmay be aligned with the leg end faces.

In addition, the U-shaped configuration of the body, i.e. theconfuration that does not have end and top walls, allows the adjustingbars of any length to be provided in the body.

The body walls having in the front part thereof a pair of divergingwedge-shaped projections and having their upper end faces located theclosest possible to the surface of a work ensure the desired jamming andretention of flux during welding in the zones upstream of the weldingbath and along the welding bath and downstream thereof up to the formedweld.

In other words, the provision of a pair of diverging wedge-shapedprojections in the front part of the body, which protrude beyond thefront end face of the forming means in the direction towards the nozzle,ensures stabilizing of preset flux pressures in the zone immediatelyadjacent to the work at various points of formation of the welding bath,i.e. along the whole length beginning from the point of location of thenozzle and up to the final formation of the weld thus greatly enhancingquality of welding.

It is preferred that the legs of the U-shaped body having thewedge-shaped projections be removable.

This construction of the legs of the body makes it possible to enlargethe range of parts being welded. It should be noted that size andconfiguration of the upper end faces of the removable legs are chosen inaccordance with welding conditions and geometry of joints being welded.

In addition, this construction of the body having the removable legswhich are provided with the diverging wedge-shaped projections in thenozzle zone allows the apparatus to be used for welding products havingdifferent shapes. It would only take to change the configuration oftheir upper end faces to fit the shape of the product.

It is preferred that the copying members in the apparatus according tothe invention comprise four wheels, the wheels being arranged in twos oneither side of the leg of the U-shaped body and positioned in a spacedrelation to each other.

This construction of the copying members in the form of four wheelsarranged on either side of the body of the forming means allowshigh-quality (without jerks, shakes and other perturbances) and stablecopying of the surface of the joint being welded to be ensured in thedirect vicinity to the welding zone, the temperature effect on the partof the body upon the copying members being eliminated which isespecially important in carrying out high-temperature welding.

The provision of the copying members in the form of wheels is mostsuitable as this facility allows welding to be carried out withsubstantial defects of surface finish.

Four copying wheels arranged in twos on either side of the legs of theU-shaped body and positioned in a spaced relation to each other ensuremaximum stability of the forming means and provide most favorableconditions for copying and for the equidistant position of the workingface of the adjusting bar with respect to the surface of the joint beingwelded. This construction of the forming means makes it possible toprovide a stable and compact apparatus featuring a very high sensitivityto fluctuations of the profile of the surface of the joint being weldedin the welding zone.

The apparatus is easy in manufacture, has small size and low weight andis comparatively inexpensive in manufacture.

Owing to the stability of all welding parameters, the apparatus ensuresenhanced welding quality in comparison with the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to its specificembodiment illustrated in the accompanying drawings, in which:

FIG. 1 schematically shows a longitudinal section view of an apparatusfor overhead submerged arc welding according to the invention;

FIG. 2 is a plan view of the apparatus of FIG. 1;

FIG. 3 is a schematic perspective view of a forming means.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An apparatus for overhead submerged arc welding according to theinvention comprises a hopper 1 (FIG. 1) containing flux 2. The hopper 1accommodates a bowl 3 for supplying flux 2 and for pressing it againstthe surface of a work 4 being welded.

The bowl 3 is in the form of a cup-shaped body, but can have any otherconfiguration as well.

The bowl 3 has an outlet port facing towards the work 4 being welded.When supplied, flux 2 leaves the bowl 3 through the outlet port and,when the bowl 3 is pressed against the work 4 being welded duringwelding, creates a flux backing which ensures preset pressures atvarious points along the joint being welded, whereby high quality ofoverhead welds is ensured.

The flux backing is in the form of a layer of flux 2 exerting a constantpressure upon the work 4 being welded, which is uniformly distributedover the entire surface area of the backing.

The inlet port of the bowl 3 is connected to a pipe 5 for supplying flux2 from the hopper 1 to the bowl 3. A port 6 in the wall of the pipe 5 isdesigned for admitting flux 2 from the hopper 1 to the pipe 5. Surplusflux 2 overflows through the bowl 3 and spills freely into the hopper 1.

Recirculation of flux 2 and its reuse are thus ensured. An auger 7 isprovided in the pipe 5 lengthwise thereof and is coupled to a rotarydrive (not shown in the drawing) by means of a gear 8. The pipe 5 andthe auger 7 form a means for supplying flux 2 and pressing it againstthe work 4 being welded.

The hopper 1 accommodates a welding head having a nozzle 9 for supplyinga consumable electrode 10, one end of the nozzle 9 being located in thebowl 3 and the other end attached to a means 11 for supplying electrodewhich supports a coil 12 mounted by means of an arm.

The hopper 1 is mounted on an arm 13 of a suspension by means of a pivotpin 14 for rotation about this pivot pin.

The bowl 3 and the pipe 5 for supplying flux 2 and the hopper 1 arerigidly interconnected and form an integral structure. A pivot joint 15having two degrees of freedom is provided in the bottom part of the bowl3 and supports a forming means a part of which is located in the bowl 3adjacent to the nozzle 9 of the welding head. The forming meanscomprises a U-shaped body 16 having its open top part facing towards thework being welded, and an adjusting bar 17 is provided inside the body16 lengthwise of the joint being welded. Two legs 18 (FIG. 2) of thebody 16 have in the front part thereof a pair of diverging wedge-shapedprojections 19. The wedge-shaped projections 19 protrude beyond thefront end face of the body 16 in the direction towards the nozzle 9(FIG. 1) and have their end faces located in the maximum vicinity to thesurface of the work being welded so as to ensure the desired jamming andretention of flux during welding at points upstream of the welding bath,lengthwise of the welding bath, and downstream of the welding bath up tothe formed weld.

Position of the adjusting bar 17 in the body 16 is vertically adjustableby means of removable inserts 20 (FIG. 3) and retainers 21 (FIG. 1). Thepivot joint 15 is mounted in the bowl 3 in such a manner that itstransverse axis is aligned with the pivot pin 14 of the hopper 1.

The legs 18 (FIG. 2) having the wedge shaped projection 19 may beremovable so as to ensure a large range of applications of the formingmeans for various sizes and diameters of products being welded.

The U-shaped configuration of the body 16 which does not have end andtop walls makes it possible to accommodate therein an adjusting bar 17of any desired length in accordance with specific welding conditions.Copying members in the form of four wheels 22 (FIGS. 2, 3) are providedoutside the body 16, the wheels 22 being arranged in twos on either sideof the legs 18 of the body 16 and being positioned in a spaced relationto each other.

The wheels 22 are positioned in the vicinity to the welding bath so asto provide optimum conditions for copying the surface of the joint beingwelded during welding.

For providing optimum conditions for carrying out overhead welding, thewheels 22 (FIG. 3) may protrude beyond the upper end faces of the legs18 of the body 16.

Placing the wheels 22 above the upper end faces of the legs 18 of thebody 16 determined preset points of engagement and conditions for theircontact with the surface of the work 4 being welded (FIG. 1) and alsoprevents the legs 18 of the body 16 (FIGS. 2, 3) from being worn.

In welding products having deviations of geometry and assemblyspecifications of the joints being welded, three wheels 22 out of four(FIG. 1) may be in contact with the work 4, and these may be any threewheels 22 out of four, the different wheels being in contact with thework surface during welding. The forming means thus remains stable atany moment and thereby enhances welding quality.

A clearance if formed during welding between the working face of theadjusting bar 17 and the surface of the work 4 being welded which isindispensable for overhead welding and which forms a so called fluxinterstice during welding. The amount of this clearance is determined inaccordance with specific welding conditions (welding parameters, shapeand size of reinforcement of the weld, flux type, and other conditions)and may be adjusted by placing the adjusting bar 17 in the body 16 andalso by means of the copying members (e.g. by varying the diameter ofthe wheels 22).

The adjusting bar 17 (FIG. 3) of the forming means may have stub pipes23 for supplying a coolant. The coolant may be in the form of water,air, antifreeze and other liquids, gases and fluid substances.

To avoid a pressure drop of flux 2 (FIG. 1) in the welding zone becauseof its spillage, a partition 24 of an elastic heat-resistant material isprovided in the space between the bowl 3 and the adjusting bar 17.

The pivot pin 14 of the hopper 1 may be provided at any point in thehopper 1 and bowl 3, but at any rate it should be located under theforming means and positioned as close as possible to the surface of thework being welded (to the plane of the contact points of the wheels 22).

The apparatus may be supported on a movable carriage by means of thesuspension arm 13, e.g. in welding longitudinal joints or on a carriageof a vertical slide (not shown in the drawings).

The apparatus is provided with counterweights 25 for controlling forcepressing the bowl 3 against the work 4 (the force of pressure of flux 2in the flux backing).

The abovedescribed apparatus functions in the following manner.

The apparatus is set up for a predetermined welding regime beforewelding by adjusting the desired pressure of flux 2 in the flux backingby appropriately positioning the counterweights 25; by adjusting theremovable inserts 20 (FIGS. 1 and 3) and retainers 21 (FIG. 1) to adjustvertical position of the adjusting bar 17, and operating conditions ofthe auger 7, welding head and other components of the apparatus are alsoadjusted in accordance with the type of the joint being welded, geometryof the joint and work 4, and the like.

The amount of clearance between the upper end faces of the legs 18 ofthe body 16 and the work 4 being welded is also set up. The adjustmentis carried out both by making choice of diameter of the wheels 22 (FIGS.2, 3) and by making choice of appropriate change legs 18.

The wheels 22 are then pressed by the suspension (not shown in thedrawings) and by a force transmitted thereby to the arm 13 (FIG. 1) andto the pivot pin 14 of the hopper 1 against the underside of the work 4being welded. Upon engagement with the work 4 and pressure of the pivotpin 14, the wheels 22 are positioned with respect to the surface of thejoint being welded, the working face of the adjusting bar 17 is set to apreset position, and position of the entire forming means supported bythe pivot joint 15 copies the surface of the joint being welded duringwelding.

This support is necessary during welding to ensure the desired swingingof the hopper 1 about the pivot pin 14 on the suspension arm 13 of thehopper 1.

The hopper 1 is pressed against the work 4 together with the bowl 3 bythe counterweights 25 rotating it about the pivot pin 14. The drive ofthe auger 7 (not shown in the drawings) is turned on, and duringrotation of the gear 8 with the auger 7, flux 2 is admitted through theinlet port 6 and pipe 5 to the bowl 3 to build up the necessary fluxpressure therein.

In welding longitudinal welds, the drive of the carriage for moving theapparatus along the joint being welded is turned on (the drive and thecarriage for moving the apparatus are not shown in the drawings). Inwelding annular joints, the movement drive is not turned on, but arotary drive for rotating the work is energized (not shown in thedrawings).

A coolant, e.g. water is supplied to the stub pipes 23 for cooling theadjusting bar 17. Water flow and its temperature are controlled inaccordance with specific welding conditions.

The supply means 11 is then turned on, and the electrode 10 is suppliedfrom the coil 12 through the nozzle 9 towards the work 4, a voltage isapplied to the electrode 10 to excite an arc. As the electrode 10 moveswith respect to the work 4, the joint is welded.

The forming means supported by the pivot joint 15 is capable of swingingin its longitudinal and transverse planes during welding so as to ensurecopying of the joint being welded by means of the wheels 22. The legs 18(FIG. 2) of the U-shaped body 16 having the wedge-shaped projections 19and the elastic partition 24 (FIG. 1) ensure retention of flux 2 in thewelding zone and stabilize its preset pressure.

The forming means in the apparatus also functions as a copying memberwhich allows position of the pivot pin 14 of the hopper 1 to remainequidistant with respect to the surface of the work 4 being welded.

Therefore, the apparatus for overhead submerged arc welding according tothe invention ensures high quality of a large range of products beingwelded owing to the maintenance of flux pressure at various points ofthe weld being produced and enhanced copying of the surface of the jointbeing welded.

The apparatus allows welding to be carried out automatically so as tosubstantially eliminate operator's participation in the welding process.

The apparatus for overhead submerged-arc welding according to theinvention may be used for welding of overhead welds of different typeswith a high-quality of reinforcement formation, especially, from thebottom side of a weld. To the most advantage the apparatus may be usedfor welding back-up and single-pass overhead welds.

We claim:
 1. An apparatus for overhead submerged arc welding,comprising: a hopper containing flux pivotally mounted on a suspensionfor rotation about a pivot pin, having a welding head provided with anozzle for supplying a consumable-electrode and means for supplying fluxand pressing it against a work being welded in a zone of the nozzle, abowl accommodated in the hopper, an end of the nozzle for supplying theconsumable electrode extending through the bowl, and a forming meanshaving an adjusting bar for providing a preset pressure at variouspoints along a joint being welded, mounted on the suspension, saidforming means having copying members and being mounted for swingingmovements in the longitudinal and transverse planes and for verticaladjustment with respect to the work being welded, the forming meanscomprising a U-shaped body having an open top part facing towards thework being welded, legs of the body having, on the side of the nozzle, apair of diverging wedge-shaped projections, the adjusting bar beingprovided inside the U-shaped body along the joint being welded, and thecopying members being placed outside the U-shaped body on either side ofits legs.
 2. An apparatus for overhead submerged arc welding accordingto claim 1 wherein the legs of the U-shaped body having the wedge-shapedprojections are removable.
 3. An apparatus for overhead submerged arewelding according to claim 1, wherein the copying members comprise fourwheels, the wheels being arranged in twos on either side of each leg ofthe U-shaped body and being positioned in a spaced relation to eachother.